This invention relates to data transmission, and more particularly for a method and apparatus for detecting the CRC format in Wide Area Network (WAN) monitoring, for example.
In Wide Area Network communication, for example with the PPP protocol, a cyclic redundancy code (CRC) is employed for error detection. The sender of a data frame calculates the CRC and includes the calculated value with the frame of data. At the receiving end, the receiver calculates the CRC based on the data and compares the calculated value with the CRC value sent by the sender.
Current practices employ both 16 bit and 32 bit CRC. It is important that the same type of CRC be employed by both the sender and the receiver of the data, in order for the error detection to operate as designed. Particularly in the case of network test and monitoring equipment, wherein a particular instrument may be used on many different specific types of networks, or may be installed by persons not familiar with the particular network or protocol configurations, the particular form of CRC that is in use may be unknown.
In accordance with the prior art, it was necessary to manually select either 16 or 32 bit CRC format with monitor and test equipment, requiring the user to have knowledge of the CRC format in use and to have the skill to make the setting properly. An incorrect CRC format would make an analyzer or other test instrument unusable.